linux-kernel - Re: splice blocks indefinitely when len

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Date:	Mon, 30 Oct 2006 14:32:54 -0500
From:	Daniel Drake <ddrake@...ntes3d.com>
To:	Phillip Susi <psusi@....rr.com>
Cc:	jens.axboe@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: splice blocks indefinitely when len > 64k?

On Mon, 2006-10-30 at 14:11 -0500, Phillip Susi wrote:
> While it should not simply hang, the splice size needs to be an even 
> multiple of the page size.

I don't think that is true, at least on this level. Firstly, splice-cp
does this:

#define BS	SPLICE_SIZE
int this_len = min((off_t) BS, sb.st_size);
int ret = splice(in_fd, NULL, pfds[1], NULL, this_len, 0);

No considerations are made regarding page size.

Secondly, the problem still exists when I increase SPLICE_SIZE to
(128*1024)

Daniel

> Daniel Drake wrote:
> > Hi,
> > 
> > I'm experimenting with splice and have run into some unusual behaviour.
> > 
> > I am using the utilities in git://brick.kernel.dk/data/git/splice.git
> > 
> > In splice.h, when changing SPLICE_SIZE from:
> > 
> > #define SPLICE_SIZE (64*1024)
> > 
> > to
> > 
> > #define SPLICE_SIZE ((64*1024)+1)
> > 
> > splice-cp hangs indefinitely when copying files sized 65537 bytes or
> > more. It hangs on the first splice() call.
> > 
> > Is this a bug? I'd like to be able to copy much more than 64kb on a
> > single splice call.
> > 
> > Thanks!
> > Daniel
> 

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